IE关闭不跳转

方法如下: 但是不跳转, 为什么了
<script>    
  function finish() 
   if   (event.clientX<=0  && event.clientY < 0||event.altKey)  {    
                           var    xmlhttp   =   new   ActiveXObject("Microsoft.XMLHTTP");   
                                  xmlhttp.open("GET",   "123.php", false);   
                                  xmlhttp.send(null);      
                     } 
</script>
<body onselectstart="return false" onUnload="finish()">